1. Field of the Invention
The present invention relates to a zoom lens having a wide angle of view and a high zooming ratio, and a camera employing the same.
2. Description of the Related Art
Digital still cameras (DSCs) are now being widely used to photograph images. A zoom lens including three lens groups having negative, positive, and positive refractive powers and with a half field angle of 29° to 32° at a wide angle and a 3× zooming ratio is commonly being used in a digital camera due to its small lens diameter or short overall length. A current silver gelatin single-lens reflex (SLR) camera using 35 mm film is equipped with standard zoom lenses having highly sophisticated functions, a focal length (wide angle) of 24 mm at a wide angle position at a half field angle of about 42° that is shortened from 28 mm at a half field angle of about 37°, and a zoom ratio of 8× at about 24-200 mm focal length that is increased from about 7× at a 28-200 mm focal length.
Thus, to achieve a wide angle and a high zooming ratio for a digital camera, a zoom lens including five lens groups with positive, negative, positive, negative, and positive refractive powers have been employed to permit flexibility in selecting a wide range of designs.
FIG. 1 illustrates a five lens group zoom lens disclosed in Japanese Laid-Open Patent Application No. 2001-350,093.
Referring to FIG. 1, the zoom lens includes first through fifth lens group Gr1 through Gr5 having positive, negative, positive, negative, and positive refractive powers that are sequentially arranged from an object side toward an image side. While the zoom lens has a high zooming ratio from 7× to 10×, it does not provide a wide angle of view because the maximum half field angle at a wide angle position is about 38°.
Another example of a five lens group zoom lens proposed in Japanese Laid-Open Patent Application No. 2003-255,228 also has a high zooming ratio from 5× to 10×. In an embodiment providing the maximum wide angle, however, a zooming ratio is about 5× for a half field angle of about 38° at a wide angle position. Thus, the zoom lens does not satisfy both wide angle and high zooming ratio requirements. Yet another example of a zoom lens presented in Japanese Laid-Open Patent Application No. 2003-287,681 provides a high zooming ratio of 10× but inadequate half field angle of only about 32° at a wide angle position.